Let's start off by mentioning that this series is very loosely based on a arcade videogame that is quite popular in Japan. As a manager, you have to nurture your favourite girl into becoming an idol. Obviously, it works with savegames etcetera.
So if you thought this series was about cute girls singing and dancing on stage and overcoming their competitors through optimism and hard work, you were wrong. It is about cute girls piloting mecha and kicking the shit out of meteors and each other! There is a sideplot that mentions idol singers, but that gets only minimal screen time... So it's kind of a weird tie-in with the game, to say the least.
But it all starts off innocently enough. Haruka gets into an audition to become an idol singer (!), and she gets through the preliminaries! She has to move to Tokyo, where a room in a dorm is reserved for her. She has to take this weird keychain-thing with her all times, and she will go through the rest of the auditions there. And so she sets off to Tokyo, but by the end of the first episode she is already in the cockpit of an iDol -- something with that one (called Imber) reacting to her keychain and/or personality.
iDols are man-made mecha that have been built around cores that were found on the moon, that are capable of generating limitless energy. Since the moon fractured, there is a lot of debris falling down (and the changed atmosphere jams cellphone reception when the script calls for it), and there is a huge network that tracks the movement of the rocks orbiting the Earth. Most countries use (nuclear) rockets to shoot 'em down when one threatens to land on their patch of the planet, but Japan doesn't want to use such technology (for obvious reasons) -- so they use the iDols!
So teenage girls are sent into space aboard mecha that are powered by something no-one really understands in order to smash big rocks into tiny fragments. There is a trick to the iDols, you see: they can only be piloted by teenage girls. (And for reasons unknown to us, the audience, almost all of the staff are teenage girls too...) There is some debate whether the iDols (or rather, their cores) are (semi-)sentient or not. Some pilots regard the iDols as mere tools because of an accident seven years ago, but others (Haruka amongst them) think that the iDols have a will of their own, and that the efficiency of the system is influenced by the relationship between the mecha and the girl piloting it. It is telling that the scientific staff and the executive staff don't seem to have an opinion one way or the other.
The whole thing kind of blows up when a rival organisation, who wants to use the iDols for their own nefarious purposes. They have an iDol of their own, you see. And the global anti-asteroid organisation has their own designs: they initiate digging up another iDol that has been embedded in a volcano on Iceland, and they replace the commander with their own mole. The commander strikes back in a most amusing way, though -- he is quite the character: resourceful and full of insight into the motivations of his enemies.
From that time on, it's not about smashing asteroids anymore -- it's about kicking enemy ass, while trying to stay out of the hot waters of the global conspiracy, and trying to recover stolen iDols, and getting to grips with betrayal and loss.
In that respect, one could regard Idolmaster Xenoglossia as a more light-hearted version of Evangelion -- the parallels are obvious. But instead of a steady decline into paranoia and despair, Idolmaster Xenoglossia manages to scramble upright again and end the series in a highly positive note.
Technically, there is nothing wrong with this series -- certainly a trend in recent anime. Especially the CGI is executed very competently.
- Very well animated, with great CGI effects;
- Fun story with lots of action.
- Bit shallow in its treatment of certain themes.
All in all, fun to watch, but not one for the top of the list. A 7.5.